Ferret erratic knocking from left hand side front.

[Malcolm Towrie]

We drove a Ferret about 15 miles to a Canada Day parade with no problem but during the parade, it started to knock once loudly when braking to a standstill. This was coming from LHS front, outside the hull. By the end of the parade, the knocking was much worse. Multiple knocks, erratic, not related to wheel speed, like someone hitting the outside of the hull with a hammer, and only when drivetrain was loaded. I could feel the impact on the hull from the inside. When coasting downhill, i.e. unloaded, there was no knocking.

No obvious loose suspension parts. Pulled the brake drum off and no breakage or loose parts.

For info, I dismantled the hub a while back to replace the brake backing plate.

Anyone experienced this ?

Malcolm

[Robin Craig]

It might sound like one thing but may be another.

I had a bevel box input bearing go (long story) that sounded like that as the input flange thwacked around as it destroyed itself.

I am sure it will reveal itself shortly in a pile of expensive broken bits

[Richard Farrant]

Hi Malcolm,
If this is what I think it is, I have dealt with it on numerous occasions, with Ferret as well a Saracen, Stalwart, Fox, etc. It could well be a metal deposit between the a tracta fork and knuckle on an outer tracta joint. Due to localised heat a pit occurs on one part and a deposit on the other and when driving in a straight line this does not create any or much noise, until you steer off centre and the pip is then not aligned with the pit and then knocking occurs. What you could do is jack up both wheels one side and get someone to turn the rear one and watch the front wheel, if you have the steering slightly one way you may notice the wheel kick as it turns. Depending on how big an area is damaged it is permissible to stone down the damaged to regain working clearance, the pit actually serves as an oil retainer, just depends how bad it is.

regards Richard

[Malcolm Towrie]

Originally Posted by Richard Farrant

Hi Malcolm,
If this is what I think it is, I have dealt with it on numerous occasions, with Ferret as well a Saracen, Stalwart, Fox, etc. It could well be a metal deposit between the a tracta fork and knuckle on an outer tracta joint. Due to localised heat a pit occurs on one part and a deposit on the other and when driving in a straight line this does not create any or much noise, until you steer off centre and the pip is then not aligned with the pit and then knocking occurs. What you could do is jack up both wheels one side and get someone to turn the rear one and watch the front wheel, if you have the steering slightly one way you may notice the wheel kick as it turns. Depending on how big an area is damaged it is permissible to stone down the damaged to regain working clearance, the pit actually serves as an oil retainer, just depends how bad it is.

regards Richard

Richard,
This noise happens when going in a straight line and only when the drivetrain is loaded. Steering left or right doesn't seem to make any difference. And it's not a regular click-click while turning like I have heard from pitting of CV joint bearing surfaces. Sounds more like what Robin is describing.

Malcolm

[Grant Hopkins]

Sounds familiar, I had a bevel box go on my Ferret in the RH rear position. It started to clunk and got rapidly worse on the way back to park it, it even locked up a couple times and I had to move it in reverse briefly to unlock and continue ahead. I wouldn't recommend driving it until you figure out exactly what is wrong, it could become a very heavy and difficult to move roadblock.

[45jim]

Insect suspension ball joints, steering joints and wheel nuts to ensure tight and serviceable. If all OK, disconnect the driveshaft from the transfer box to the suspect bevel box. Drive the Ferret around a parking lot to see if the noise is related just to the suspect wheel station. If noise stops suspect u-joint on driveshaft or bearing on bevel box input or transfer box output or the transfer box itself. If still knocking from the wheel station you know your problem is the wheel station itself, remove the outer hub cover and remove the sun gear and replace the cover. Move the vehicle carefully in a straight line. The tracta joint and bevel box will be disengaged and should remain stationary. If the noise goes away your problem is there and you will have to remove the wheel station to further diagnose. If the noise is still there you will have to dig further into the hub itself as this may be a bearing failure or a broken gear in the reduction hub.

[Malcolm Towrie]

Originally Posted by Grant Hopkins

Sounds familiar, I had a bevel box go on my Ferret in the RH rear position. It started to clunk and got rapidly worse on the way back to park it, it even locked up a couple times and I had to move it in reverse briefly to unlock and continue ahead. I wouldn't recommend driving it until you figure out exactly what is wrong, it could become a very heavy and difficult to move roadblock.

Grant, what had actually failed in the bevel box?

Malcolm

[Malcolm Towrie]

Originally Posted by Robin Craig

It might sound like one thing but may be another.

I had a bevel box input bearing go (long story) that sounded like that as the input flange thwacked around as it destroyed itself.

I am sure it will reveal itself shortly in a pile of expensive broken bits

Robin,
Did you hear the input bearing get noisy before the flange thwacking started? Or did the bearing just collapse, like they do if the cage suddenly breaks up?

Because in our case, the front left wheel station was running smoothly and quiet until the knocking started quite suddenly.

It's off the road until this is fixed, which may be take a while due to other priorities.

Malcolm